Two-dimensional input devices for inputting handwritten data and text, sketching and drawing into a host computer are relatively well known. Most of these applications require the transfer, in real time, of a pen or stylus position on a tablet to a host computer for storage, processing or display. In these applications, it is desirable to have both a handwritten record of the activity and a record in a memory. It is also desirable to perform these functions without the need for a host computer, thus permitting portable and field use of the input device.
Currently available pen-based computer systems are self contained and utilize a central processing unit and an operating system. An active tablet or a passive tablet is a peripheral device to a host computer, which records coordinate position information. All known systems have serious limitations.
Currently available active tablets can be functionally classified as inductive, transparent digitizing, resistive, acoustic, laser scanning and the like. These tablets have deficiencies in resolution, accuracy, robustness, cost, uniform resistivity, drift, size, weight, reliability, and the like. For example, inductive tablets have problems with electrical noise and field distortion from nearby metallic objects. These tablets must be attached to a host computer which limits portable and field use.
Prior art passive tablets typically fall into two categories. The first category is the well known mouse device which uses a surface to enter relative positional data into a system. The second category normally utilizes a stylus pickup device, which provides relative or absolute position as the moving stylus is passed over a tablet surface containing grid lines in the X and Y directions. Current systems of the second category suffer from lack of resolution for applications such as handwriting and graphical drawing.
Prior art encoded paper using bars of printed lines generally falls into two classes. In the first class, bars are placed adjacent to each other at spaced regular or irregular intervals, are aligned vertically and are sequenced in one direction. Methods for reading encoded information from conventional bar codes and for decoding the bar code information are known in the art. This technique is used for inventory identification, pricing, adding the prices of goods and other applications. The bar code reader includes a light source for illuminating the elements of the bar code. Reflected light is directed with a series of optical elements onto an image photosensor.
U.S. Pat. No. 4,731,526 issued Mar. 15, 1988 to Knoll et al discloses a technique for determining navigation data from a map. A line code grid is imprinted on the map or on a separate foil. The line code includes vertical and horizontal lines that may differ as to width, distance, color, and the like. Fluorescing and phosphorescing inks are suggested. Infrared absorbing or reflecting substances are also disclosed. The line code is used to determine the position on a map using a light pen. In addition, the line code can be implemented as raised portions which are mechanically sensed.
Handwriting input techniques are disclosed in U.S. Pat. No. 4,947,156 issued Aug. 7, 1990 to Sato et al; U.S. Pat. No. 5,051,736 issued Sept. 24, 1991 to Bennett et al; U.S. Pat. No. 4,839,634 issued Jun. 13, 1989 to More et al; U.S. Pat. No. 4,856,077 issued Aug. 8, 1989 to Rothfjell; U.S. Pat. No. 4,814,760 issued Mar. 21, 1989 to Johnston et al; U.S. Pat. No. 4,860,372 issued Aug. 22, 1989 to Kuzunuki et al; U.S. Pat. No. 4,794,634 issued Dec. 27, 1988 to Torihata et al; U.S. Pat. No. 4,723,836 issued Feb. 9, 1988 to Kono et al and U.S. Pat. No. 4,448,837 issued May 15, 1984 to Ikeda et al.
French Patent No. 2,423,522 discloses information on fluorescent markings in the near infrared. The French patent discloses an ink, consisting of pigments from the rare earth group, which absorbs or emits in the infrared. These inks are designed for indexing documents such as envelopes, postal checks, tickets and similar applications.
It is a general object of the present invention to provide methods and apparatus for reading and storing coordinate information representative of the instantaneous position of a pen on a writing surface.
It is another object of the present invention to provide a writing paper having a prerecorded pattern of pixels, each pixel containing encoded location information which identifies an absolute and unique coordinate location on the paper.
It is a further object of the present invention to provide an information input system for simultaneously recording written information on encoded paper and recording the written information in a memory.
It is a further object of the present invention to provide a pen and paper information recording system which has high resolution, is accurate, reliable and low in cost, and allows multiple users to use several pens on one paper.